Step 1: Parts list

a 10mm LED (I recommend, that you use a diffuse LED. I live in Denmark and the diffuse LEDs aren't available here, so I just used a waterclear type)

a CR2032 lithium coincell battery.

a Neodymium (NdFeB) disc magnet.

a LM3909 LED Flasher circuit

an Electrolytic capacitor (the bigger the capacitor is, the slower the LED flashes. I figured out, that a 100µF works fine. It will flash the LED at approx. 2.5Hz, while a 220µF will flash it with 1Hz.

Step 2: Solder the capacitor onto the LM3909

Now it's time to Solder the capacitor onto the LM3909 (see all the pictures)

Step 3: Solder the LED onto the LM3909

Now it's time to solder the LED onto the LM3909 (see pictures)

Step 4: Cut off the unused leads of the LM3909

Cut off the unused leads of the LM3909, so they don't short circuit.

Step 5: Solder two leads onto the LM3909

Now it's time to Solder two leads onto pin 4 and 5 of the LM3909.

Step 6: Mold it (optional)

You can "mold" the circuit using a hot glue gun. This will make it water proof and shock resistant.

Step 7: Tape the battery and the magnet onto the circuit

Tape the battery and the magnet onto the circuit, just like you would do with an ordinary LED Throwie

Hi there. Only picked up your reply now :-( Apologies!! Would appreciate you finding out how many LM3909 IC's your local supplier has and at what cost. These chips have been unobtainable her in South Africa for the last 7 years :-((( Thanks and regards.

How much time should the batterie be alive??? I've made the same circuit and the first batterie ruined out in 1 week. I used a 100 µf / 25v capacitor and a ordinary red led diode. I've read the lm3909 datasheet and with a 1,5 v AA batterie it should be working for at least 6 month. What could be wrong??

Hello there This is interesting but I do not know if you know, but there are in the market built in flashing LED and the cost of those are very cheap, the bad thing is I believe they comes in red and yellow but for the instance u can add this flashing leds in series to another color LED you want. You can find them in Digikey online. But is good though.

Thanks. I know there are some LEDs with a build-in flashing circuit but: 1. The flashing 10mm LEDs aren't available in diffused version 2. With this you can control the flashrate by changing a capacitor 3. The flashing LEDs aren't available where I live and I'm not old enough to buy stuff from the Internet in other countries.

Hello my friend. Keep the good track line with your invents, the less I want to do is to take you out of this precious career. Some times is difficult to find components in other areas but still you can order this items sometimes for free in some online sites (e.g. www.texasinstruments.com). But do not worries it will came the day that you can buy your own items. I did not looking for 10mm flashing diffused leds but I'm sure there will be. Anyways thank you for your comments and if there is anything that is on my hands to help you let me know.

I know what you mean, I salvage parts too. Three times a year, there is a big market nearby me where they sell used and new stuff: clothing, electronics, cups dishes and stuff like that. I often buy some cheap electronics there.